Here's the stand glued up with the last of the clamps still on before finishing. It'll need to dry for a day, then sanding and primer.

The printer sits on top of the pad (It's a huge old HP Business Inkjet 2250; yes the footprint really is that crazy shape) and the little shelf on top is for the ink tubes and the wireless access point belonging to the printer. It all sits above/behind so that the tubes are out of the way and there's plenty of gravity feed.



More once the glue is dry.

I'm finally back to finish this thread up. Work has been busy and I hadn't had time to finish putting everything together. I can't find my tripod right now, so these might be a little blurrier than the last batch...

Paint on the stand is dry. The color scheme is chosen to match the printer (beige and gray... doesn't get much more 'business printer' than that).





Last edited by xiphmont on Fri Apr 24, 2009 12:57 am; edited 1 time in total

Oh, it's probably worth disassembling and taking photos of a dead printhead. I had wondered early on if the printheads have a filter inside, as I didn't want to have to build one into my CIS. There are other nitfy surprises inside.

First a few views of the outside before ripping it open. Bottom view of the actual ink nozzles. To the left of the nozzles is an ink filling port sealed with a hard rubber ball as a stopper like on the ink cartridges. The rubber is much harder and the fit much much tighter than on the ink cartridges however, There's also no lip inside to prevent it from being accidentally pushed all the way into the head. More later on the inside view.

View of the contact pads, 'smart chip' and flexible traces running to the nozzles. The nozzles, interestingly, aren't part of the strip itself. They're etched onto a bar of crystalline silicon, chip-style, and seperately bonded into the head. That answers the question 'how so few traces?'... it's not a passive system. The nozzles are active logic interfaced right into the real world, and the printer apparently issues commands to the nozzles rather than just pushing current.

Unfortunately I didn't grab a pic of the exposed nozzles before accidentally shattering the nozzle chip into tiny pieces. Oops.

View from the top. Hmmm... that little flap with the 'hp' and arrow on it looks like it's just glued on. is this our port of entry?

Unfortunately not. It appears to be a manufacturing convenience and only covers the passage from the needle inlet to the rest of the cartridge. Looking more closely though, the entire plastic top is simply a flat, glued on piece.

The glue used to assemble the heads is quite brittle and will pop apart perfectly if torqued just right. Unfortunately, the plastic is also quite brittle.

The heads are as mechanically complex inside as the cartridges!

This assembly is a ink flow regulator. The HP Business Inkjets have pumped/pressurized ink feeds internally, so the printhead catridges have to be able to shut off ink flow when full.





Last edited by xiphmont on Fri Apr 24, 2009 12:59 am; edited 1 time in total

Pop the spring off and all becomes clear. The plastic 'flaps' sandwich a sealed plastic air bladder that's exposed to the outside through a pinhole. As the printhead uses up ink, air is drawn in through the pinhole, filling the plastic bladder, forcing the plastic flaps apart and opening the flow valve.

Another view of the flow regulator fully disassembled. This is a rather nicely engineered system. No wonder this printer runs like new at ten years old. Sigh, HP really used to design good stuff.